Dual control system

ABSTRACT

At least two rotating means are rotatably mounted on an axle in juxtaposition with variable resistance elements disposed between the rotating means. Support means including a base portion and having means extended from the base portion hold the rotating means and the variable resistance elements in spaced relation.

United States Patent I 1 i 1 i961 88 1; 64 fi 1511 40 i *i 32 Fr 54 36 1 l 56 t 1 190; i 1

Primary Examiner-Lewis H. Myers Assistant ExaminerGerald P. Tolin AttorneysRichard H. Childress and Robert F. Meyer ABSTRACT: At least two rotating means are rotatably mounted on an axle in juxtaposition with variable resistance elements disposed between the rotating means. Support means including a base portion and having means extended from the base portion hold the rotating means and the variable resistance elements in spaced relation.

PATENTEU m2 l97l SHEET 2 UF 2 INVENTORS GEORGE o. PUERNER CHARL s BURNS BY 2 g W ATTORNEY v DUAL CONTROL SYSTEM Generally, in radio and in stereo sets many variable resistors are used. Such variable resistors are frequently called volume controls" whether or not they are used for the specific purpose of controlling volume. In the typical set, several of these controls are situated behind a panel with rotating means for operating the controls being situated in front of the panel for convenient manipulation.

In the construction of such volume controls, many problems must be met. Not the least among such problems is that of compactness. Generally speaking, in applications such as stereophonicdevices, that is stereo devices, the amount of space available for such control units is limited. This is especially true in applications of stereo devices in automobiles, for example. Not only must there be a minimum number of parts for such control unit, but the parts must be capable of being easily assembled. This becomes extremely difficult in units such as stereo devices where separate amplifier systems must be controlled for tone, volume and balance.

As previously noted, such control units are usually mounted on an instrument panel with some suitable rotating means being made readily available to the operator for operating the controls. In many applications such rotating means include thumbwheels which are mounted outside of the panel for easy accessibility. With this construction, however, the control elements themselves have been remote from the rotating means such that the unit looses much of the desirable compactness. More specifically, prior art control units having thumbwheels to operate the control elements remote from the elements utilize complicated intermediate drive means, such as cooperating gears, to actuate the elements in response to rotation of the thumbwheels. This leads to a bulky arrangement and in addition, because of the number of parts and their interrelation, mechanical difficulties often occur.

The present invention is concerned with a variable resistor control system wherein several variable resistors are used, and has as one of its objects a provision of such a variable resistor control unit which is compact with a minimum number of parts.

Another object of the invention is to provide a control system wherein the rotating means for the control system are thumbwheels placed in close juxtaposition.

Still another object of the invention is to provide a control system having thumbwheels for operating the control system wherein the thumbwheels are rotatably mounted on a common axle.

Still another object of the invention is the provision of a control system having thumbwheels rotatably mounted on an axle in close juxtaposition with the variable resistance elements disposed between the thumbwheels.

Yet another object of the invention is the provision of a control system having thumbwheels rotatably mounted on an axle in close juxtaposition wherein the variable resistance elements are carried by circuit boards disposed between the thumbwheels.

Another object of the invention is the provision of a control system having thumbwheels rotatably mounted on an axle in close juxtaposition wherein electrical contact elements cooperating with variable resistance elements are carried by the thumbwheels and wherein at least one of the thumbwheels drives an on-off switch.

A further object of the invention is the provision of a control system having thumbwheels mounted on an axle in close juxtaposition wherein at least one of the thumbwheels has locating means for establishing a desired operation condition.

Yet another object of the invention is the provision of a support means for a control system wherein the support means carries at least two thumbwheels for the control system and variable resistance elements in spaced relation between the thumbwheels.

Another object of the invention is the provision of a support means for a control system having a base portion remote from the control elements and having means extending from the base portion to hold the variable resistance elements in spaced relation between a pair of thumbwheels.

Still another object of the invention is the provision of a support means for a control system wherein the support means includes a U-shaped member having slots for carrying circuit boards for variable resistance elements, at least a portion of these circuit boards being disposed between the thumbwheels.

Yet another object of the invention is the provision of a stereo device wherein the control system for the device includes variable control elements for tone, volume, and balance, and being disposed between a pair of thumbwheels operating such control elements.

These and other objects of the invention and the nature thereof will become apparent from the following description considered in conjunction with the accompanying drawing and wherein like reference numbers describe elements of a similar function.

For illustrative purposes, the invention will be described in conjunction with the accompany drawings in which:

FIG. I is a perspective view showing two pair of controls mounted to an instrument panel;

FIG. 2 is an exploded view of a control according to the invention illustrating the arrangement of its parts;

FIG. 3 is a transverse section through the control assembly of the present invention;

FIG. 4 is a plan view of a printed circuit board with a switch mounted thereon; and

FIG. 5 illustrates a modification of the control assembly adapted for controlling devices remote from the assembly.

Generally speaking, the objects of the invention are accomplished by providing a control system which comprises at least two rotating means rotatably mounted on an axle, electrical contact elements and cooperating resistance elements or paths on which the electrical contact elements ride disposed between the rotating means with support means holding the rotating means, the resistive elements and the contact elements in spaced relation. An on-off switch for the control is operated by drive means including a gear means surrounding the axle. In addition, a locating means operating off of one of the rotating means is provided to establish a desired operating condition.

Referring now to the drawings and more specifically to FIG. 1, an instrument panel 10 is shown with openings 12 to receive rotating means 14, 14", 18 and 18" for operating the substantially similar controls 14 and 18 respectively. Also mounted to the panel 10 and operable by one of the sets of rotating means is an indicator 16. The controls 14 and 18 may be connected to a mounting means 17 disposed behind the panel.

The control 18 is illustrated in FIG. 2 with all of the corresponding parts exploded for purposes of clarity. It can be seen that the control 18 includes a support means 20, having a four-sided base portion 22, including a pair of support sides 24 and 26 and integrally connected at their ends by two notched sides 28 and 30. The notched sides 28 and 30 are interconnected at one of their edges by a U-shaped extension member 32. The extension 32 and sides 28 and 30 have provided on their contiguous faces grooves or slots 34, 34' and 34" to receive boards 36, 36 and 36" respectively. Each board is substantially identical in shape and is adapted to receive a different combination of components to provide a different function. Also included in the support means are legs which engage base portion 22 in a manner hereinafter described.

The first board 36 receives an arcuate resistive element or path 38 on face 37 of the board by way of staples 40. Also received on the face 37 is a ground ring 42, and a plurality of electrical terminals 44 which are staked to the board 36 with the staking means entering into a printed circuit pattern 46 (shown on board 36") on the opposite face 39to provide an electrical path to the terminals 44 from the ground ring 42 and resistive element 38. It should be noted that the shape and arrangement of the terminals 44 are such that a plug-in unit (not shown) can be easily connected thereto. Such plug-in unit could include, for example, the female terminal plugs for the amplifier means of the speakers.

The board 36' is substantially similar to board 36. As shown, a snap action switch means 48 with electrical terminals connected thereto has been added between the terminals 44 and resistance element or path 38 on surface 37 The switch 48 may be any suitable switch, particularly a snap-switch as shown, which includes an overcenter spring 50 which is pivotally carried on a first terminal 51. One end of spring 50 is movable into and out of engagement with a second terminal 52 to complete an electrical circuit. The overcenter spring 50 is movable and compressible by way of a cam 54 (FIG 3), disposed on a recessed face of gear 58. The board 36 also carries terminals 44, resistive strip 38, and ground ring 42 similar to that of board 36. A third board 36" is shown inverted in relation to 36 and 36' and due to the fact that the printed circuit 46 of board 36' and printed circuit 46 of 36" are in close proximity to each other, an electrically insulative member 56 is placed therebetween to prevent any short circuiting. Such insulative member may be fabricated of an insulative plastic such as nylon, for example. The insulating member is mounted on board 36" by way of two rivets 56'. Also located on the board 36" is a locating means, such as a detent means 57. The detent means includes a resilient offset blade 59, having a substantially flat end 61 fixed to board 36" by way of rivets 63. The free offset end 65 of blade 59 protrudes through an aperture 69 so as to allow a dimple 71 on end 65 to ride the face 73 of thumbwheel68 (one of the rotating means 18 and 18" of FIG. 1) so as to move the dimple in and out of a detent cavity 84. This detent means is provided to allow the operator to feel the proper location of the thumbwheel so as to have an indication of when the proper setting of the electrical components used in conjunction with the thumbwheel has been reached.

As previously stated the cam 54 of FIG. 3 located on a gear 58 is positioned to actuate the snap switch 48. The gear is rotatably mounted on a post 60 which is located between boards 36 and 36' and securely staked thereto, and is in mesh with a drive gear 62. Gear 62, which is rotatably coupled to thumbwheel 68' carries a movable contact 64. As previously noted, the boards 36, 36 and 36" are positioned in their respective grooves 34, 34' and 34" in frame 32, with the gears 58 and 62 located between boards 36 and 36' with insulative member 56 located between boards 36 and 36" to thereby provide a compact stack of electrical components. With reference to- FIGS. 2 and 3, thumbwheels 68 and 68' are rotatably mounted on an axle 66 through bushings 90 and 90' with the bushings passing concentrically through the entire stack through the rings 42 in boards 36, 36' and 36" and apertured boss 67 in drive gear 62. Since each of the thumbwheels are substantially identical, the discussion of any one of the indicated parts is intended to apply to both the wheels.

Continuing with reference to FIGS. 2 and 3, the thumbwheels include two parts, a hub 72 and an annular ring 74 having serrated edges 75. The annular ring 74 has a recessed cavity 76. Projecting into the cavity 76 from the perimeter of the ring 74 is a cam boss 78. Provided on the boss 78 are two stop faces 80 and 80' which lie in the same arcuate path as that of the stop projections 82 on U-shaped member 32. Therefore, it can be seen that the annular displacement of the thumbwheels 68 and 68 is governed by the location of the stop faces 80 and 80 and the stop projections 82. This controls the amount of displacement of contacts 64 on resistive paths 38. Also located on the boss 78 is the detent cavity 84,

' previously described. It should be understood that there may be more than one of such detent cavity, and that the location of the cavities need not be limited to the boss 78, but may be disposed around the ring 74.

The second part of the thumbwheel includes a hub 72. The hub 72 is provided with an annular rim portion 86 which is molded to a lip 77 which forms an opening 88 in the ring 74.

Located on the inner surface of the hub is a pair of bosses 70 which project from the hub 72 to which are heat staked or otherwise attached electrical contact elements 64. Previously noted bushing 90 and clutch lugs 92 also project from the hub 72. Formed on the opposite face of the hub 72 and molded therewith is a bevel gear 94 which maybe used for various purposes, an example of which will be discussed in conjunction with FIG. 5.

Although the drawings illustrate a thumbwheel which has an outer ring and an inner hub molded in the outer ring, it will be understood by those skilled in the art that the hub and the ring could be molded separately from each other and snapped together to thereby provide a unitary thumbwheel. Or, alternatively, they could be molded at the same time together in the same mold to thereby provide an integral part. In addition, it should be noted that at least the hub 72 should be fabricated from an electrically insulative material such as nylon.

The thumbwheels 68 and 68 are placed over the opposite ends 66" and 66 of axle 66. Bushings 90 and 90' on the thumbwheels 68 and 68' are so dimensioned that when they are in proper position, the bushings are in face-to-face contact with each other as shown in FIG. 3. This automatically determines the proper spring tension of contacts 64 on thumbwheels 68 and 68. It can be seen that as wheel 68' is positioned over axle 66, the boss 90' passes through apertured boss 67 on drive gear 62. As is more clearly shown in FIG. 2, boss 67 has located at one of its extremities a pair of annular recesses 98 which align with the clutch lugs 92 (shown on thumbwheel 68) on the thumbwheel 68' to provide a positive drive between the thumbwheel 68' and drive gear 62. One of the recesses 98 on the boss 67 is of a greater arcuate length than the outer recess 98, which corresponds to one of the clutch lugs 92 on the thumbwheel 68 to thereby assure accurate annular alignment between the thumbwheel 68' and the drive gear 62.

As shown in FIGS. 2 and 3, after the axle 66 and thumbwheels 68 and 68 are in their proper position, a pair of cantilevered legs 100, having notches 102 at one end thereof is received in annular grooves near the ends 66 and 66" on the axle 66. Therefore both thumbwheels 68 and 68' and gear 62 are trapped between the two legs 100. The opposite ends of legs are secured to the sides 24 and 26 of base portion 22 to form a yoke for carrying axle 66. This is achieved by the shoulders 104 on leg 100 being placed in abutting contact with stops 106 which project from sides 24 and 26. The extended neck portion 108 of leg 100 is positioned directly over the notched opening 110 in the sides 24 and 26 so as to properly align and secure the cantilevered legs 100. After the legs 100 have been properly positioned over the frame sides 24 and 26, the neck portions 108 are clenched over the sides 24 and 26 as shown in FIG. 3 so as to engage notch 110. Due to the threepoint contact in securing the legs 100 to the base portion, a proper alignment of the axle 66 and the base portion 22 is obtained. More specifically, the thumbwheels with the control elements disposed between them, are both radially and axially aligned with respect to the base portion 22.

In operation, thecontrol 18 is mounted to a suitable control panel 10 (FIG. 1), by way of mounting brackets 112 (FIG. 2) and mounting means 17. The control is then properly connnectedto any audio equipment such as a radio, television, phonograph, etc. The thumbwheels, which may be independently operable, could, for example, drive the volume control for two banks of audio outputs such as stereo phonograph or stereo radio.

As the thumbwheel 68' is rotated by the operator's thumb in a direction to correspond to the arrow 114 in FIG. 4, the wheel in turn drives the drive gear 62 which is in mesh with cam-carrying gear 58. The cam 54, upon rotation in the opposite direction from that of arrow 114, compresses the overcenter spring 50 until which time the high point of the cam passes the free end of the overcenter spring 50. At this time, the free end of the spring 50 will move in the opposite direction from that of the cam 54 and will continue at a rapid speed until it comes to rest against a point on terminal 52. Thus a conductive path is obtained between terminals 52 and 51 by way of overcenter spring 50. The device is turned off when the cam 54, through movement of the thumbwheel 68, is rotated in the opposite direction from that of arrow 114 and thereby reverses the movement of the overcenter spring 50 and in the manner previously described until the spring returns to the position as shown in F IG. 4.

After the switch has been turned on, any further rotation of the thumbwheel 68"will increase the output volume of the audio equipment which is electrically connected to resistive elements 38 on boards 36 and 36' due to the change in the arcuate displacement of the contact elements 64 disposed on the underside of both the wheel 68 and the drive gear 62. There fore, simultaneously, the volume output to two different amplifiers such as used in stereo sound systems is obtained through the movement of only one thumbwheel.

Thumbwheel 68 operates a locating means for achieving a desired condition such as a substantial equal volume output of the amplifiers of a stereo. Such balance is provided through the use of a locating means which includes a detent means 57. Thumbwheel 68 (dial means 18" of FIG. 1) is rotated in either direction until dimple 71 of resilient ofi'set blade 59 engages detent cavity 84 of thumbwheel 68. With the detent means so engaged, the volume output of the stereo amplifiers is substantially the same. Such engagement, however, is nonlocking such that further rotation of the thumbwheel 68 disengages dimple 71 from the detent cavity 84 so that volume output from the individual amplifier can be varied.

Referring now to FIGS. 1 and 5, a construction similar to that of the control 18 is used for control 14, which could, for example, control the tone outputs of the stereo and operate an indicating dial 16. However, as will be apparent, since different functions are being performed, certain elements of the control may be eliminated. The driving of the indicator 16 is achieved by the use of a second bevel gear 95 in mesh with the bevel gear 94' which may be integral with the hub 72 of thumbwheel 68" (dial means 14 of HQ. 1). The second bevel gear 95 is operable through a window 97 in leg 100. The bevel gear 95 is fixedly secured to a shaft 99, with the shaft being joumaled for rotational movement by way of a bearing tang 101, lying in the window 97 in leg 100. Shaft 99 is limited from any axial movement by way of the bent-up tang 101 being sandwiched between the bevel gear 95 and a C-ring 103 on the shaft 99. It should be noted that to assure proper mesh between the gears, they should be resiliently held. This is accomplished through coil spring 115 positioned around the bushing 90" and compressed between the wheel hub 72 and the drive gear 62" to thus provide sufficient resilient pressure necessary to obtain good mesh between gears 94 and 95. Rotation of thumbwheel 68" thus causes rotation of shaft 99 through gears 94 and 95. The rotation of shaft 99 may then drive indicator means 16 through suitable mechanical linkage means (not shown). Should the thumbwheel 68" carry contact elements such as contacts 64 associated with thumbwheels 68 and 68', coil spring 115 would not be necessary since the resiliency of the contact elements would provide the necessary resilient pressure to mesh gears 94 and 95.

Dial means 14" of FIG. 1, is in the present embodiment of the invention a dummy in that there are no components being controlled through its operation. It should be understood, however, that such dummy" rotating means could be readily adapted for operating various components in the manner previously described.

Thus there is described a modular control unit wherein the various-components of the unit can be readily adapted to the operation or control of various electrical functions. The components of the units, such as the variable resistance elements and their cooperating electrical contacts are disposed between the close, juxtapositioned rotating means or thumbwheels thus making the unit very compact and easy to assemble in a supporting panel. The various elements of the device which provide these features and others are recited in the following appended claims.

What I claim is:

l. A control system which comprises a pair of thumbwheels rotatably mounted about an axle in close juxtaposition, variable resistance control elements including electrical contact elements carried by said thumbwheels and cooperating with resistive elements disposed between said thumbwheels, said control elements adapted to be operable by said thumbwheels; support means, said support means including a base portion disposed remote from said thumbwheels, and a U-shaped member extending from said base portion holding said thumbwheels and said control elements in spaced relation.

2. A control system according to claim 1 wherein said thumbwheels comprise an annular ring and a hub disposed in an aperture of said ring.

3. A control system according to claim 2 wherein gear teeth are formed as part of said hub.

4. A control system according to claim 2 wherein said electrical contact elements are carried by said hub.

5. A control system according to claim 3 wherein said thumbwheel is axially spring biased.

6. A control system according to claim 1 wherein electrical terminals extend from the end of said board opposite said aperture, and electrical ground means surround said aperture.

7. A control system according to claim 6 wherein said electrical terminals are plug-in type terminals.

8. A control system according to claim 1 wherein said circuit boards are separated by an electrically insulating plate sandwiched between said boards.

9. A control system according to claim 1 further including switch means and drive means connecting said switch means with said rotating means.

10. A control system according to claim 9 wherein said switch means is carried by a circuit board provided with an aperture adapted to receive said axle.

11. A control system according to claim 9 wherein said drive means comprises a drive gear driven by one of said thumbwheels, said drive gear engaging gear means including cam means biasing said switch means.

12. A control system according to claim 11 wherein said drive gear is driven by said thumbwheel through at least one recess formed on a boss of said drive gear, said recess engaging corresponding lugs extending from said thumbwheel.

13. A control system according to claim 1 wherein stop means are provided on said thumbwheels to limit the angular displacement of said contact elements.

14. A control system according to claim 13 wherein said stop means comprises stop faces provided on a boss of the rim of said thumbwheels, said faces engaging stop projections provided on said support means.

15. A control system according to claim 1 wherein locating means for establishing a desired operating condition is provided on said thumbwheels.

16. A control system according to claim 15 wherein said locating means is a detent means comprising a detent cavity provided on a boss of said thumbwheel and a dimple provided on a movable blade engaging said cavity.

17. A control system according to claim 1 wherein said U- shaped member has slots for carrying circuit boards carrying variable resistance elements.

18. A control system according to claim 1 wherein said means holding said rotating means and said control elements in spaced relation includes a yoke engaged with said axle.

19. A control means according to claim 1 wherein said axle passes through circuit boards carrying variable resistance elements, and wherein said U-shaped member extending from said base portion having slots carries said circuit boards.

20. A control system comprising:

a. a support means, said support means including a base portion and a U-shaped member extending from said base portion, said U-shaped member having slots extending substantially along the length of the inner face of said member,

b. a plurality of circuit boards disposed in said slots, each having an aperture disposed toward the U-shaped portion of said U-shaped member,

c. said circuit boards having resistive elements, electrical ground elements, and electrical terminals disposed thereon,

d. said U-shaped member disposed between a pair of close juxtaposition thumbwheels rotatably mounted on an axle passing through said circuit boards, and said U-shaped member,

e. electrical contact elements carried by said thumbwheels,

said contact elements cooperatively engaging said resistive elements,

f. switch means carried -by one of said circuit boards, and drive means including a drive gear rotatably mounted on said axle and means connecting said gear to one of said thumbwheels, i

g. and holding means extending from said base portion engaging the ends of said axle.

21. A control system according to claim 20 wherein said thumbwheels are rotatably mounted on said axle though bushings integrally connected to said thumbwheels and extending along substantially the entire length of said axle.

22. A control system according to claim 2l=wherein an insulative plate is sandwiched between at least two of said circuit boards, said plate including an aperture adapted to receive said axle.

23. A control system according to claim 20 wherein stop means are provided on said thumbwheels, said stop means engaging stop means on said U-shaped member.

24. A control system according to claim 20 wherein at least one of said circuit boards carries a movable blade including means engaging detent means formed on one of said thumbwheels.

25. A control system comprising:

a. a support means, said support means including a base portion and a U-shaped member extending from said base portion,

b. said U-shaped member disposed between a pair of thumbwheels rotatably mounted on an axle passing through said U-shaped member, at least one of said thumbwheels having a gear means disposed on the outer face of said thumbwheels,

c. holding means extending from said base the ends of said axle, I

d. and means to spring bias said thumbwheel having said gear means disposed on said outer'face axially alongsaid axle.

26. A control system according to claim 25 wherein said spring bias means comprises a coil spring disposed between said thumbwheels and surrounding said axle.

27. A control system according to claim 25 wherein said gear means is a bevel gear engaging a second bevel gear carried by a rotating shaft.

28. A control system according to claim 27 wherein said holding means has an opening through which said second bevel gear extends to mesh with said first named bevel gear, and wherein tang means extend from said holding means, said tang means having an aperture through which said shaft carrying said second bevel gear is rotatably mounted.

portion engaging 

1. A control system which comprises a pair of thumbwheels rotatably mounted about an axle in close juxtaposition, variable resistance control elements including electrical contact elements carried by said thumbwheels and cooperating with resistive elements disposed between said thumbwheels, said control elements adapted to be operable by said thumbwheels; support means, said support means including a base portion disposed remote from said thumbwheels, and a U-shaped member extending from said base portion holding said thumbwheels and said control elements in spaced relation.
 2. A control system according to claim 1 wherein said thumbwheels comprise an annular ring and a hub disposed in an aperture of said ring.
 3. A control system according to claim 2 wherein gear teeth are formed as part of said hub.
 4. A control system according to claim 2 wherein said electrical contact elements are carried by said hub.
 5. A control system according to claim 3 wherein said thumbwheel is axially spring biased.
 6. A control system according to claim 1 wherein electrical terminals extend from the end of said board opposite said aperture, and electrical ground means surround said aperture.
 7. A control system according to claim 6 wherein said electrical terminals are plug-in type terminals.
 8. A control system according to claim 1 wherein said circuit boards are separated by an electrically insulating plate sandwiched between said boards.
 9. A control system according to claim 1 further including switch means and drive means connecting said switch means with said rotating means.
 10. A control system according to claim 9 wherein said switch means is carried by a circuit board provided with an aperture adApted to receive said axle.
 11. A control system according to claim 9 wherein said drive means comprises a drive gear driven by one of said thumbwheels, said drive gear engaging gear means including cam means biasing said switch means.
 12. A control system according to claim 11 wherein said drive gear is driven by said thumbwheel through at least one recess formed on a boss of said drive gear, said recess engaging corresponding lugs extending from said thumbwheel.
 13. A control system according to claim 1 wherein stop means are provided on said thumbwheels to limit the angular displacement of said contact elements.
 14. A control system according to claim 13 wherein said stop means comprises stop faces provided on a boss of the rim of said thumbwheels, said faces engaging stop projections provided on said support means.
 15. A control system according to claim 1 wherein locating means for establishing a desired operating condition is provided on said thumbwheels.
 16. A control system according to claim 15 wherein said locating means is a detent means comprising a detent cavity provided on a boss of said thumbwheel and a dimple provided on a movable blade engaging said cavity.
 17. A control system according to claim 1 wherein said U-shaped member has slots for carrying circuit boards carrying variable resistance elements.
 18. A control system according to claim 1 wherein said means holding said rotating means and said control elements in spaced relation includes a yoke engaged with said axle.
 19. A control means according to claim 1 wherein said axle passes through circuit boards carrying variable resistance elements, and wherein said U-shaped member extending from said base portion having slots carries said circuit boards.
 20. A control system comprising: a. a support means, said support means including a base portion and a U-shaped member extending from said base portion, said U-shaped member having slots extending substantially along the length of the inner face of said member, b. a plurality of circuit boards disposed in said slots, each having an aperture disposed toward the U-shaped portion of said U-shaped member, c. said circuit boards having resistive elements, electrical ground elements, and electrical terminals disposed thereon, d. said U-shaped member disposed between a pair of close juxtaposition thumbwheels rotatably mounted on an axle passing through said circuit boards, and said U-shaped member, e. electrical contact elements carried by said thumbwheels, said contact elements cooperatively engaging said resistive elements, f. switch means carried by one of said circuit boards, and drive means including a drive gear rotatably mounted on said axle and means connecting said gear to one of said thumbwheels, g. and holding means extending from said base portion engaging the ends of said axle.
 21. A control system according to claim 20 wherein said thumbwheels are rotatably mounted on said axle though bushings integrally connected to said thumbwheels and extending along substantially the entire length of said axle.
 22. A control system according to claim 21 wherein an insulative plate is sandwiched between at least two of said circuit boards, said plate including an aperture adapted to receive said axle.
 23. A control system according to claim 20 wherein stop means are provided on said thumbwheels, said stop means engaging stop means on said U-shaped member.
 24. A control system according to claim 20 wherein at least one of said circuit boards carries a movable blade including means engaging detent means formed on one of said thumbwheels.
 25. A control system comprising: a. a support means, said support means including a base portion and a U-shaped member extending from said base portion, b. said U-shaped member disposed between a pair of thumbwheels rotatably mounted on an axle passing through said U-shaped member, at least one of said thumbwheels having A gear means disposed on the outer face of said thumbwheels, c. holding means extending from said base portion engaging the ends of said axle, d. and means to spring bias said thumbwheel having said gear means disposed on said outer face axially along said axle.
 26. A control system according to claim 25 wherein said spring bias means comprises a coil spring disposed between said thumbwheels and surrounding said axle.
 27. A control system according to claim 25 wherein said gear means is a bevel gear engaging a second bevel gear carried by a rotating shaft.
 28. A control system according to claim 27 wherein said holding means has an opening through which said second bevel gear extends to mesh with said first named bevel gear, and wherein tang means extend from said holding means, said tang means having an aperture through which said shaft carrying said second bevel gear is rotatably mounted. 